Kinetic of the effect of PACAP on PC12 cell differentiation. A, cells were exposed to PACAP (100 nM) for durations ranging from 1 min to 48 h and the percentage of cells with neurites, number of neurites per cell, and total neurite outgrowth was measured 48 h after the beginning of the treatment. B, cells were exposed to PACAP (100 nM) for durations ranging from 1 min to 48 h, and cell quantification was performed 48 h after the beginning of the treatment. **, P < 0.01, *** P < 0.001 versus control.